In communication networks various communication network devices are connected to each other in order to exchange communication data. Typically, when exchanging data, data rates are relatively high, e.g. above 1 Gb/s, and optoelectronic cables are therefore used. Pluggable transceivers, e.g. SFPs, are commonly applied to convert the electrical signals into optical signals, and vice versa. However, there exist also pluggable transceivers which communicate data with other pluggable transceivers as electrical signals. Typically, these kind of pluggable transceivers transform outgoing electrical signals into other electrical signals of another format to be conveyed via communication cables.
In this description “pluggable transceiver” will be used to denote any suitable pluggable transceiver for connecting a transmission cable to a communication device. For instance, the pluggable transceivers could be implemented as: SFP transceivers, defined in SFF-8074i (Small FormFactor); Improved Small Pluggable Formfactor transceivers or SFP+ transceivers, defined in SFF-8432; QSFP (Quad Small Pluggable Formfactor) transceivers, XFP (10 Gigabit Small Form Factor Pluggable), or CFP (C Formfactor pluggable)
With reference to FIG. 1, which is a schematic overview, a situation where SFPs are exchanging data will now be described according to an example.
Two communication network devices 100, 102 are arranged to exchange data. In this example the communication network devices 100, 102 are implemented as an RE (Radio Equipment) and a REC (Radio Equipment Control) arranged within a Radio Base Station. However, SFPs may be used in a plurality of different communication scenarios, for instance at routers or other communication network devices which communicate data at high data rates. Each communication network device 100, 102 comprise a printed circuit board 106 to which SFPs 104 will be connected. Both the SFPs 104 and the printed circuit boards 106 have electrical contacts arranged thereupon to connect the SFPs 104 to the printed circuit boards 106. On the printed circuit boards 106 cages 108 are arranged to receive the SFPs 104 and fixate the contacts of the SFPs 104 to the contacts of the printed circuit boards 106, when the SFPs are inserted into respective compartments of the cages 108.
Cages are commonly provided with different numbers of compartments where each compartment is arranged to receive one SFP, e.g. a cage could be provided with 1, 2, 4, or 8 compartments, etc. In order to shield the SFPs electrically and prevent the SFPs from being affected by electromagnetic interference from their surroundings, the cages are generally made of metal. For instance, in radio base stations, there are communication network devices arranged which emit radio magnetic radiation and give rise to electromagnetic interference. The cages are therefore arranged to protect as well the SFPs from being affected by disturbing electromagnetic radiation from surrounding communication devices, as for protecting the surrounding communication devices from being affected by the SFPs.
Within this description the term “printed circuit board assembly” will be used to define a printed circuit board comprising a cage mounted thereon.
FIG. 2 is a schematic illustration of an SFP 200 and a transmission cable 202, according to an example. The SFP 200 is arranged to receive communication data from a transmitting communication network device (not shown) via the transmission cable 202, and input the communication data into a receiving communication network device 210 (illustrated with dotted lines). The SFP 200 will therefore be connected via a transceiver contact 204 to a matching board contact 212 of the receiving communication network device 210. Typically, the board contact 212 is located in a cave of a printed circuit board assembly of the communication network device.
When cages are mounted on a printed circuit board, they are commonly manually placed on the printed circuit board before being attached to the printed circuit board, e.g. by soldering, wiring, or glueing.
FIG. 3 is a schematic illustration of a cage commonly used today. The cage 300 in this example comprises four compartments 302, and each compartment 302 is arranged to receive one respective pluggable transceiver, when the cage 300 is attached to a printed circuit board and operating. In order to enable the cage 300 to be mounted on a printed circuit board there are a plurality of pins 304 arranged on the cage 300, where the pins 304 fit into corresponding holes of the printed circuit board. When mounting the cage 300 on the printed circuit board, an assembler places the cage 300 onto the printed circuit board before the pins 304 are soldered to the printed circuit board. In order to achieve proper fastening of the cage 300, there may be a large number of pins 304 arranged. To achieve efficient production of cages 300, the pins 300 are commonly designed from the same working piece as the cage 300. In general, the cages 300 are placed manually on the printed circuit board and due to the large amount of pins there is a risk for damaging the pins 302 when mounting, e.g. the pins may be bent, which may result in deterioration of attachment or shielding properties.
Furthermore, operating SFPs generate excesses heat, which in a narrow space of the cage could deteriorate operating conditions of the SFPs.
In order to achieve reliable working temperature of the pluggable transceivers, excessive heat will be removed, and cages are generally provided with ventilating holes 306, which are punched or drilled in the material of the cages.
When printed circuit board assemblies are arranged in communication network devices, the cages are inserted through holes in a bezel or a clam shell. In order to fixate the cages to he bezels/clam shells, the cages are commonly provided with resilient tabs 308.
A typical process for manufacturing the cage 300 according to the described example is to punch out five parts of a working peace: an upper part, a bottom part, and three intermediate compartment walls. Furthermore, the process comprises to punch ventilation holes 306, resilient tabs 308, and means for fixating the parts to each other. Commonly, such means for fixating is implemented as further tabs of the working peace which will be folded when assembling the parts. In this example, the upper part is folded to form two side walls of the cage 300. Finally, the parts are assembled into the resulting cage 300, e.g. by folding the further tabs, or by soldering, etc., which could then be mounted on a printed circuit board.
Thus, there are many operational and assembling steps to be performed when constructing cages, where some of the steps cause risk for damaging small parts of the working peaces. Damaged parts may give rise to deterioration of electro magnetic compability (EMC) or improper fastening. Cages which do not fulfil EMC properties may have to be discarded and replaced, which could be causes additional costs.
With reference to FIG. 4, which is a schematic overview, the steps for mounting a printed circuit board assembly will now be described according to an example.
A printed circuit board assembly 400 is to be inserted in a so called clam shell 410. In this example, the printed circuit board assembly 400 comprises a printed circuit board 404 and a cage 402 mounted thereon. The opening of the cage 402 will be introduced through a corresponding hole 412 in the clam shell 410 when the printed circuit board assembly 400 is mounted in the clam shell 410. To enable the printed circuit board assembly 400 to be mounted into the clam shell 410, the clam shell 410 will typically require an additional internal space, such that the printed circuit board assembly first is immersed into the clam shell 410, before being pushed towards the hole 412 of the clam shell 410.
As indicated above, there is a risk for damaging parts of the cages when mounting the cages into clam shell 410, e.g. the mounting tabs 308. Damaged parts may achieve that the printed circuit board assemblies do not operate properly, or that the cages will not shield electromagnetic radiation properly. In environments where pluggable transceivers are applied, the requirements for EMC are commonly strict, since the communication network devices as well as the pluggable transceivers emit electromagnetic radiation and may affect each other.
Thus, there is a need for a robust connection arrangement for pluggable transceiver, which is able to produce efficiently.